While it is evident that the LH secretory system of the domestic cat can be influenced by external stimuli (especially copulation in the female) detailed analysis of the neuroendocrine regulation of gonadotropin secretion in this species has not been developed. Such an analysis will require sensitive methods for the measurement of cat LH in sequential serum samples and, as a primary goal of this project, we are validating an existing LH RIA system (the ovine-ovine LH radioimmunoassay of Niswender et. al.) for use with the cat. The system has been used to demonstrate a rapid increase in serum LH concentration following copulation in the intact (spontaneously estrous) female. We propose to extent those preliminary observations to include more animals, and to the study the effects of several sequential matings on the magnitude of the LH response. Other studies involving the castration response, inhibition of episodic LH secretion in the castrated cat, and the response to synthetic LHRH under a variety of endocrine conditions are also planned.